The Portal d’Andorra, the old Andorra Gate, is the main vestige preserved from the ancient complex of city walls and fortified strongholds that protected and encircled La Seu d’Urgell. It is a pointed arch portal which connects Carrer dels Canonges with Carrer Major.

The defences were structured on the basis of a tower with the gate, or portal, opening on the ground floor. When the building lost its military function, once a new exterior walled enclosure had been built, the tower was re-adapted for use as a civilian residence. With the expansion of the walled enclosure, from the late 14th century, the Andorra gate was situated in the upper part of Carrer de Capdevila, so the old gateway became known as the Portal vell d’Andorra, or Old Andorra Gate.

In the second half of the 14th century, the original medieval enclosure was enlarged to meet new needs, both demographic and of war. In this period of the Early Middle Ages, the walled area of La Seu d’Urgell became very strong, with sections of the wall that enclosed the whole of what is now known as the historic centre, reinforced by towers of square and semicircular section. During the modern age, the wall would be enhanced with bastions on which to place artillery.